For the production of carbonyl compounds through oxidation of olefins, the Hoechst-Wacker process is well known (see, Japanese Patent Publication No. 7869/1961). Palladium chloride/copper chloride-base catalyst out of Wacker type catalysts as used in the Hoechst-Wacker process are of high activity and used in oxidation of ethylene or propylene. These catalysts, however, have a disadvantage in that when used in oxidation of olefins containing 4 or more carbon atoms, they are liable to yield chlorinated compounds. In addition, catalysts comprising palladium (Pd) and one or more elements such as iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), etc. are known (see, Japanese Patent Publication No. 6643/1976 and Japanese Patent Application Laid-Open No. 43686/1978). These catalysts are capable of suppressing the formation of halogenated compounds as described above but have a disadvantage of being inferior in activity.
In order to overcome such problems of the prior art, the present inventors have already proposed a catalyst having rhodium and manganese supported on a carrier (Japanese Patent Application No. 177551/1982). This catalyst, however, is not sufficiently satisfactory in that the selectivity of the desired carbonyl compound is somewhat low.
The present invention is therefore intended to provide more improved catalyst compositions for use in oxidation of olefins. As a result of further investigations, it has been found that when there are employed novel catalysts comprising rhodium, manganese, and at least one of the Group IIIA elements (excluding the actinium series elements) of the Periodic Table, the selectivity of the desired carbonyl compound, particularly methyl ethyl ketone is markedly increased and undesirable chlorinated compounds are not produced. It has further been found that addition of zinc compounds to the above-described catalyst compositions enables to increase the durability or the life time of the resulting catalysts.